Field of the Invention
The present invention relates to a link actuating device for a robot joint portion, an industrial machine and the like that is used for speedily and precisely performing operations, such as handling of articles and complex processing, in a three-dimensional space over a wide range. Particularly, the invention relates to a link actuating device that is suitable for, in the medical field, being mounted around a human joint portion for use in assisting the recovery of the function of the joint and the movement thereof, and a platform that includes a link actuating device of this kind and supports an optical device such as a camera so that the angle of the optical device can be changed in at least two directions.
Description of Related Art
As the above-described link actuating device, there have been proposed configurations in which an input side link hub and an output side link hub are connected by a three-link-chain link mechanism including four revolute pairs so as to permit the attitude of the output side link hub to be changed relative to the input side link hub (e.g., Patent Documents 1 and 2). The three-link-chain link mechanism composed of the four revolute pairs includes input side and output side end links rotatably connected to the input side and output side link hubs, respectively, and an intermediate link rotatably connected to the input side and output side end links. Patent Document 1 discloses an example in which, in a geometric model obtained by representing a link mechanism by straight lines, the portion on the input side and the portion on the output side relative to the central portion of the intermediate link have shapes that are mirror symmetrical, and an example in which they have shapes that are point symmetrical. Patent Document 2 discloses an example in which the portion on the input side and the portion on the output side have shapes that are point symmetrical.
Conventional link actuating devices, including Patent Documents 1 and 2 described above, have three sets of link mechanisms. The reason for this is that, in the case of forming the link mechanism by only links, the minimum number of link mechanisms required to define the attitude of the output side link hub relative to the input side link hub is three.
Furthermore, some link actuating devices are mounted around a human limb joint portion for the purposes of the assistance of movements, including passive movement of bending and stretching of a joint portion and walking or the like, for the angle correction around the affected area as a result of a limb fracture and the function recovery. For example, Patent Document 3 discloses a device that controls CPM devices used in the medical field, and the device controls one degree of freedom of the CPM devices. All the conventional CPM devices described in Patent Document 3 have one degree of freedom in the bending angle direction of the joint portion. Patent Document 4 discloses a mounted type assisting device that is mounted to the side surface of a leg to assist the movement of the leg, and the device assists only bending and stretching movements of the leg.
In addition, platforms including a link actuating device of this type are proposed in Patent Documents 5, 6, and 7, for example. Patent Document 5 proposes a two-degree-of-freedom platform capable of changing the angle of an optical device such as a camera in two directions, namely, a tilt direction (vertical rotational direction) and a pan direction (horizontal rotational direction). Patent Document 6 proposes a three-degree-of-freedom platform capable of changing the angle of the optical device also in an inclined direction, in addition to the tilt direction (vertical rotational direction) and the pan direction (horizontal rotational direction). Patent Document 7 proposes a three-degree-of-freedom platform having a structure constituted by one spherical pair.